Iridology: it’s dangerous pseudo-diagnostic

A position paper of the Associazione Pazienti Malattie Oculari (APMO) evaluated IRIDOLOGY. Here is its abstract:

Iridology is an alternative diagnostic practice that claims to identify systemic diseases and organ dysfunction through visual inspection of iris features, including pigmentation patterns, crypts, furrows, and discolorations. Despite its continued presence within complementary and alternative medicine, iridology has not been incorporated into mainstream medical practice. This review critically examines iridology from an ophthalmologic perspective, addressing its historical origins and epistemological foundations, proposed mechanisms, biological plausibility, and clinical evidence. A systematic appraisal of the available literature, including the most recent government-commissioned evidence evaluation, demonstrates a consistent lack of diagnostic accuracy, reproducibility, and pathophysiological rationale. The ethical and clinical implications of iridology use are discussed, with particular attention to the risk of delayed diagnosis and patient misinformation. Based on the totality of evidence, iridology cannot be supported as a diagnostic or screening tool in ophthalmology or general medicine.

In the article itself, the authors drew the following, detailed conclusion: Iridology is a diagnostic practice whose foundational maps were constructed through uncontrolled post hoc observation, without anatomical, physiological, or embryological basis. Decades of controlled investigation – including the most recent government-commissioned systematic review applying GRADE methodology [16] – have failed to demonstrate diagnostic accuracy beyond chance, and no credible mechanism links iris features to systemic organ pathology.

A scientifically rigorous appraisal must acknowledge several nuances: the evidence base itself is limited in volume and methodological quality; a single study using automated photodensitometry produced one marginally significant finding; and one recent unblinded study reported high sensitivity at the cost of unacceptably low specificity. These exceptions do not alter the overall conclusion but illustrate that further high-quality prospective blinded trials would strengthen the evidentiary record.

Based on the available evidence, the Associazione Pazienti Malattie Oculari endorses the following key messages:

• Iridology should not be used or endorsed as a diagnostic or screening tool in ophthalmology or general medicine.
• The epistemological foundations of iridology (chart construction through uncontrolled post hoc correlation) are incompatible with scientific validation regardless of clinical trial results.
• Computer-aided iridology represents a technological advance that has not yet addressed the underlying validity problem and should not be regarded as validated.
• Patient inquiries should be addressed with empathy, scientific clarity, and a clear distinction between genuine ocular signs of systemic disease and unsupported claims.
• Ophthalmologists have a professional responsibility to safeguard the scientific integrity of ocular diagnostics and to protect patients from practices with potential for harm.

All of this confirms what I have been saying and writing for several decades. My recent book BIZARRE MEDICAL IDEAS has a chapter on iridology and his inventor. Here is its abstract:

Ignaz von Peczely (1826-1911) was born into a noble Hungarian family. He became a lay homeopath but later decided to study medicine in Vienna where he graduated aged 36. He then had a thriving medical practice in Vienna. Peczely’s discovery of iridology allegedly goes back to his childhood when he noted discolourings in the eye of an injured owl. Throughout his professional life, Peczely promoted iridology with some success. Other practitioners took over the mantle and made sure iridology is popular to the present day.

What needs stressing, I feel, is the fact that iridology is not just a mere folly, it is dangerous! False negative and false positive diagnoses – iridology is unable to deliver anything else – carry serious, sometimes life-threatening risks.